Speech processing is performed in numerous areas for a wide variety of applications, such as voice recognition, speech compression, and digital telephony to name a few examples. Speech processing is a complex art, often relying on sophisticated algorithms and equipment. In many instances, and particularly real time applications performed by equipment with limited processing ability, it is not possible to dedicate all signal processing resources to speech processing. At the same time, it is often the case in such instances that speech processing is used to detect the presence of speech in a signal in order to take some action. For example, in digital speech compression, rather than process and store periods of silence in a speech segment, when speech is not present, only minimal processing is necessary. However, to do so requires the ability to determine when a speech segment is speech and when it is silence. In many instances fricative portions of speech can appear to be background noise, and thus may be omitted, or not detected properly.
At the same time, other areas of speech processing are becoming more complex. For example, speech encoding is now routinely used to compress speech for mobile communication systems. This type of speech processing is referred to as vocoding. In vocoding speech information is sampled and framed. An example of frame could be a 30 millisecond section of speech. Through the process of vocoding, as is known in the art, the frame is mapped to one of a plurality of symbols representing parts of speech, and other parameters are generated corresponding to the frame of speech so that another apparatus decoding the vocoded signal can reconstruct the sampled section of speech. In order to perform further processing, such as speech detection, by conventional means, would require more sophisticated, and therefore more expensive equipment. In consumer equipment it is preferable to reduce material cost, and therefore there is a need for a simple and reliable method of detecting speech.